The effect of L-3, 4-dehydroproline on the antitumor activity and toxicity of bleomycin.

Pulmonary fibrosis is a serious side effect that limits the therapeutic utility of bleomycin (BLM). Recently, it has been demonstrated that L-3, 4-dehydroproline (DHP), a proline analog, significantly reduced the extent of pulmonary fibrosis in rats administered BLM intratracheally. The present studies were performed to determine the effect of DHP on the oncolytic and toxicologic effects of BLM. DHP (25 mg/kg/day) administered sc concomitantly with BLM (4 mg/kg/day) for 9 consecutive days following a sc inoculation of B16 melanoma cells in BDF1 had no effect on tumor growth inhibition by BLM when tumor growth rate was assessed by tumor volume and by tumor weight. To determine the effect of DHP on the toxicity of BLM, DHP (25 mg/kg/day) and BLM (10 mg/kg/day) were administered to Sprague-Dawley rats for 5 consecutive days followed by 2 days of rest and 5 additional days of drug administration. BLM administration produced decreased body weight gain, acute leukocytopenia, delayed elevation in blood nitrogen levels, chronic lung and kidney disease, and alopecia. Animals administered BLM plus DHP had a similar toxicologic profile. One striking difference was that no animal administered BLM plus DHP developed alopecia, whereas five of eight rats administered BLM alone displayed this untoward effect. These results suggest that DHP neither diminishes the oncolytic activity nor exacerbates the nonpulmonary toxicity of BLM, DHP would appear, therefore, to be a potential candidate as an antifibrotic adjunct to BLM therapy.